Some power transmission mechanisms, for example automotive transmissions, employ planetary gearsets having planet pins to support planetary gears for rotation. In some applications, it is desirable to rivet or stake the planet pins in place by deforming and enlarging one or both end of the planet pin. The end configuration of some known pins used in riveted or staked applications have a deep, centrally located conical recess formed in the staked end. The recess penetrates into the center portion of the body of the planetary pin. This configuration requires that the planetary pin be made longer to accommodate the conical recess, undesirably occupying more axial space within the transmission.
Some power transmission mechanisms, for example automotive transmissions, employ planetary gearsets requiring lubrication for reliable operation and thermal stability. In some transmissions, planet pins have fluid passages drilled through the pin body to deliver a lubrication fluid, for example oil, from a source such as an “oil dam” or a “lube catcher” to a raceway of a planetary bearing during operation. The flow of the oil requires rotation of the planetary gear carrier to generate centrifugal head to push the oil into the planet pin fluid passages.
In some new automotive transmissions, operating conditions exist in which the planetary gear carrier is stationary, making lubrication using the centrifugal head impossible. An alternate lubrication system is therefore needed.
Some current planetary gear systems may include a planet pin having a lubrication port formed at an acute angle through the pin wall to provide a flow of oil with a passage formed along the longitudinal axis of the pin. Drilling at an angle through bearing-grade steel can be a multi-step and complicated drilling operation.
Other systems require a series of intersecting passages selectively sealed with plugs to direct the flow. These systems require that the planet pin be fixed in the carrier for position and retention. Staking or riveting the planet pin in place is the preferred assembly method for some production requirements. However, current planet pins with intersecting passages cannot be staked due to the location of some passages, therefore increasing the assembly time and complexity. In known planetary gear systems with staked or riveted pins, the pins are made longer than necessary in order to accommodate the staking operation, thus undesirably taking up axial space in the transmission.
Therefore a need exists for a planet pin with oil passages for use in a planetary gear system that can be staked or riveted in place. A need also exists for a planet pin configured to be staked in place without increasing the length of the pin.